Intestine immune homeostasis after alcohol and burn injury

Reduced Expression of miR-146a Potentiates Intestinal Inflammation following Alcohol and Burn Injury

MicroRNAs (miRNAs) are small noncoding RNA molecules that negatively regulate gene expression. Within the intestinal epithelium, miRNAs play a critical role in gut homeostasis, and aberrant miRNA expression has been implicated in various disorders associated with intestinal inflammation and barrier disruption. In this study, we sought to profile changes in intestinal epithelial cell miRNA expression after alcohol and burn injury and elucidate their impact on inflammation and barrier integrity. Using a mouse model of acute ethanol intoxication and burn injury, we found that small intestinal epithelial cell expression of miR-146a is significantly decreased 1 d following injury. Using in vitro studies, we show that reduced miR-146a promotes intestinal epithelial cell inflammation by promoting p38 MAPK signaling via increased levels of its target TRAF6 (TNFR-associated factor 6). Furthermore, we demonstrate that in vivo miR-146a overexpression significantly inhibits intestinal inflammation 1 d following combined injury and potentially supports intestinal barrier homeostasis. Overall, this study highlights the important impact that miRNA expression can have on intestinal homeostasis and the valuable potential of harnessing aberrant miRNA expression as a therapeutic target to control intestinal inflammation.

Curcumin promotes renewal of intestinal epithelium by miR-195-3p

ETHNOPHARMACOLOGICAL RELEVANCE

Turmeric (Curcuma longa) has been used to treat gastrointestinal disorders in the Indian Ayurvedic medical system. According to the theory behind traditional Chinese medicine, turmeric can be distributed in the spleen meridian, for which it has been used as a digestive aid. Curcumin (Cur), a natural polyphenol compound originally derived from turmeric, has anti-inflammatory activity and can assist in treating inflammatory bowel disease.

AIMS OF THE STUDY

To investigate curcumin's protective effects on intestinal epithelium and explore the underlying miR-195-3p-related mechanisms.

MATERIALS AND METHODS

The miR-195-3p mimics were used to over-express miR-195-3p. The in vitro effects of Cur and miR-195-3p on the intestine were shown utilizing intestinal cryptlike epithelial cell line-6 (IEC-6) cells. By fasting for 48 h, an intestinal mucosal atrophy model of SD rats was created in vivo. Cur (25 or 50 mg/kg) was assessed for its protective effect on intestinal epithelium. Glycyrrhetinic acid (GA) with an intestinal protective effect reported in our previous research was adopted as a positive drug for the in vivo and in vitro bioactivity evaluation since there is no universally positive drug for either intestinal mucosal restitution or miR-195-3p modulation.

RESULTS

Cur protects the intestinal epithelium and promotes its repair after injury via down-regulating miR-195-3p. In vitro experiments showed that Cur inhibited the apoptosis of IEC-6 cells, stimulated their growth, and down-regulated the level of miR-195-3p in cells. When miR-195-3p was overexpressed, the viability of IEC-6 cells decreased while the apoptosis rate increased. All the above detrimental effects were alleviated after curcumin intervention. Moreover, Cur reversed the effect of miR-195-3p on its downstream occludin. In vivo, results showed that 48-h fasting impaired the integrity of the small intestinal mucosa (abnormal crypt structure and reduced goblet cell number), which was ameliorated by Cur treatment. In addition, the Cur treatment reversed both the increased expression level of miR-195-3p and decreased levels of ki-67 and occludin caused by fasting.

CONCLUSIONS

Cur could promote the proliferation and repair after injury of the intestinal mucosa by down-regulating miR-195-3p.

The role and therapeutic potential of gut microbiome in severe burn

Severe burn is a serious acute trauma that can lead to significant complications such as sepsis, multiple organ failure, and high mortality worldwide. The gut microbiome, the largest microbial reservoir in the human body, plays a significant role in this pathogenic process. Intestinal dysbiosis and disruption of the intestinal mucosal barrier are common after severe burn, leading to bacterial translocation to the bloodstream and other organs of the body, which is associated with many subsequent severe complications. The progression of some intestinal diseases can be improved by modulating the composition of gut microbiota and the levels of its metabolites, which also provides a promising direction for post-burn treatment. In this article, we summarised the studies describing changes in the gut microbiome after severe burn, as well as changes in the function of the intestinal mucosal barrier. Additionally, we presented the potential and challenges of microbial therapy, which may provide microbial therapy strategies for severe burn.

PRP8-Induced CircMaml2 Facilitates the Healing of the Intestinal Mucosa via Recruiting PTBP1 and Regulating Sec62

BACKGROUND

Multiple organ dysfunction syndrome (MODS) occurs in the gastrointestinal tract and injured intestinal mucosa is the anatomical basis for various diseases. The expression of circular RNAs (circRNAs) is implicated in many diseases; however, the role of circRNAs in intestinal mucosal injury is yet to be discovered. Our preliminary gene microarray analysis revealed a novel circular RNA, circMaml2, with a significant intestinal mucosal protection effect. Its expression was found to decrease in severely burned intestinal mucosal tissue, whereas its overexpression might facilitate the reconstruction of the injured intestinal mucous membrane.

METHODS

The function of circMaml2 in cell proliferation and migration was studied in MC38 cells. The repair function of circMaml2 was tested on the intestinal mucosa of mice. RNA-binding protein polypyrimidine tract-binding protein 1(PTBP1) was selected by pull-down assay and mass spectrometry (MS). RNA immunoprecipitation (RIP) was performed to confirm the binding of circMaml2 and PTBP1 and to study PTBP1 and its downstream target, early B-cell factor 1(Ebf1). Bioinformatics software forecast analysis and dual-luciferase reporter assay were performed to ascertain miR-683 and Sec62 as the downstream targets of circMaml2 and miR-683, respectively. Furthermore, PRP8 was discovered to promote the biogenesis of circMaml2.

RESULTS

CircMaml2 promotes cell proliferation and migration of MC38 cells and the repair of the intestinal mucosa of mice. This effect is brought about by combining with PTBP1 to improve Ebf1 and interacting with miR-683 to regulate Sec2. Furthermore, PRP8 was discovered to promote the biogenesis of circMaml2.

CONCLUSIONS

This is the first reported study of the effect of circMaml2 on intestinal mucosal repair.

IL-23 Promotes Neutrophil Extracellular Trap Formation and Bacterial Clearance in a Mouse Model of Alcohol and Burn Injury

Our previous studies have shown that ethanol intoxication combined with burn injury increases intestinal bacterial growth, disrupts the intestinal barrier, and enhances bacterial translocation. Additionally, studies show that Th17 effector cytokines IL-17 and IL-22, which are dependent on IL-23, play important roles in maintaining intestine mucosal barrier integrity. Recent findings suggest neutrophils are a significant source of IL-17 and IL-22. We determined the effect of ethanol and burn injury on neutrophil IL-17 and IL-22 production, as well as their ability to phagocytose and in bacterial clearance, and whether these effects are modulated by IL-23. Mice were given ethanol 4 h prior to receiving ∼12.5% total body surface area burn and were euthanized day 1 after injury. We observed that intoxication combined with burn injury significantly decreases blood neutrophil phagocytosis and bacteria killing, as well as their ability to produce IL-17 and IL-22, compared with sham vehicle mice. The treatment of neutrophils with rIL-23 significantly increases IL-22 and IL-17 release and promotes expression of IL-23R, retinoic acid-related orphan receptor γt, Lipocalin2, and Nod-like receptor 2 following ethanol and burn injury. Furthermore, IL-22- and IL-17-producing neutrophils have enhanced neutrophil extracellular trap formation and bacterial killing ability, which are dependent on IL-23. Finally, although we observed that peritoneal neutrophils harvested after casein treatment are functionally different from blood neutrophils, both blood and peritoneal neutrophils exhibited the same response to rIL-23 treatment. Together these findings suggest that IL-23 promotes neutrophil IL-22 and IL-17 production and their ability to kill bacteria following ethanol and burn injury.

Subacute toxicity of mesoporous silica nanoparticles to the intestinal tract and the underlying mechanism

The biological safety of mesoporous silica nanoparticles (MSNs) has gradually attracted attention. However, few studies of their toxicity to the intestine and mechanism are available. In this study, their primary structures were characterized, and their subacute toxicity to mice was investigated. After 2 weeks of intragastric administration of MSNs, they significantly enhanced serum ALP, ALT, AST and TNF-α levels and caused infiltration of inflammatory cells in the spleen and intestines. MSNs induced intestinal oxidative stress and colonic epithelial cell apoptosis in mice. Intestinal epithelial cells exhibited mitochondrial ridge rupture and membrane potential decrease after MSN treatment. Additionally, MSNs increased ROS and NLRP3 levels and inhibited expression of the autophagy proteins LC3-II and Beclin1. MSNs significantly changed the intestinal flora diversity in mice, especially for harmful bacteria, leading to intestinal microecology imbalance. Meanwhile, MSNs influenced the expression of metabolites, which were involved in a range of metabolic pathways, including pyrimidine metabolism, central carbon metabolism in cancer, protein digestion and absorption, mineral absorption, ABC transport and purine metabolism. These results indicated that the subacute toxicity of mesoporous silicon was mainly caused by intestinal damage. Thus, our research provides additional evidence about the safe dosage of MSNs in the clinical and food industries.

6-Formylindolo (3, 2-b) Carbazole (FICZ)-mediated protection of gut barrier is dependent on T cells in a mouse model of alcohol combined with burn injury

6-Formylindolo (3, 2-b) Carbazole (FICZ) is a ligand of aryl hydrocarbon receptor (AHR) which regulates Th17 release of IL-17 and IL-22 production. Earlier, we showed that ethanol combined with burn injury suppresses Th17 responses and disrupts intestinal barrier leading to increased gut bacterial growth and translocation. Since IL-22 is known for its role in intestinal barrier maintenance, we determined whether treatment of mice with FICZ restores T cell IL-22 release and protects intestine barrier following ethanol and burn injury. Wildtype and Rag1-/- mice were gavaged with ~2.9 g/kg ethanol or water, and given a ~12.5% total body surface area burn. Mice were given FICZ (5 μg) in resuscitation fluid. FICZ treatment of wildtype mice normalized IL-22 and IL-17 in lamina propria and spleen T cells, as well as increased CYP1A1 expression in spleen T cells. This was accompanied by improved gut motility, decreased copy number of small intestine total bacteria and Enterobacteriaceae, attenuation of intestinal tissue levels of IL-6, KC, IL-18, decreased apoptosis, and prevention of gut leakiness following ethanol and burn injury. However, FICZ treatment of Rag1-/- mice did not improve any of the parameters listed after ethanol and burn injury. Additional data generated using mice treated with recombinant IL-22 alone or in combination with anti-IL-18 antibody suggest that full protection of gut barrier integrity requires both IL-18 inhibition and IL-22 restoration following ethanol and burn injury. Together our findings suggest that AHR ligand FICZ may have better therapeutic potential for maintenance of gut barrier function after ethanol and burn injury.

Rhubarb-Aconite Decoction (RAD) Drug-Containing Serum Alleviated Endotoxin-Induced Oxidative Stress Injury and Inflammatory Response in Caco-2 Cells In Vitro

Rhubarb-Aconite Decoction (RAD), a famous Chinese medicine prescription, has been widely used for treating intestinal injury. However, the effect of RAD on intestinal epithelial cells is unclear. The aim of this study was to investigate the effects of RAD drug-containing serum on the oxidative stress injury and inflammatory response induced by endotoxin (ET) in Caco-2 cells in vitro. Lipid peroxide malondialdehyde (MDA), lactate dehydrogenase (LDH), caspase-11, tumor necrosis factor-α(TNF-α), interleukin-3(IL-3), and cytokeratin (CK)18, adenosine triphosphate (ATP) activity, and intracellular free calcium ion levels were measured. The results showed that ET triggered the activation of caspase-11 and the massive release of TNF-α, increased the inhibitory rate of cell growth, MDA, and LDH expressions in Caco-2 cells. Moreover, RAD drug-containing serum could inhibit caspase-11 activation, decrease the release of TNF-α and IL-3, reduce intracellular free calcium ion, and enhance CK 18 expression and ATP activity. These novel findings demonstrated that ET-induced oxidative stress injury and inflammatory response of Caco-2 cells were improved by RAD drug-containing serum, indicating that RAD may be a good choice for the treatment of intestinal injury.

Evaluation of intestinal injury, inflammatory response and oxidative stress following intracerebral hemorrhage in mice

Intestinal injury is a common complication following intracerebral hemorrhage (ICH), which leads to malnutrition, impaired immunity and unsatisfactory prognosis. Previous studies have revealed the pathogenesis of intestinal injury following traumatic brain injury using ischemic stroke models. However, the effects of ICH on intestinal injury remain unknown. The present study aimed to investigate the pathological alterations and molecular mechanism, as well as the time course of intestinal injury following ICH in mice. Male C57BL/6 mice were randomly divided into the following seven groups (n=6 mice/group): Control group, which underwent a sham operation, and six ICH groups (2, 6, 12 and 24 h, and days 3 and 7). The ICH model was induced by stereotactically injecting autologous blood in two stages into the brain. Subsequently, intestinal tissue was stained with hematoxylin and eosin for histopathological examination. Small intestinal motility was measured by charcoal meal test, and gut barrier dysfunction was evaluated by detecting the plasma levels of endotoxin. Quantitative polymerase chain reaction (qPCR), immunohistochemistry and ELISA analysis were performed to evaluate the mRNA and protein expression levels of inflammatory cytokines [interleukin (IL)‑1β, IL‑6, tumor necrosis factor‑α, intercellular adhesion molecule 1, monocyte chemotactic protein 1 and chemokine (C‑C motif) ligand‑5] in intestinal tissue and serum. Furthermore, intestinal leukocyte infiltration was detected by measuring myeloperoxidase activity. Oxidative stress was indirectly detected by measuring reactive oxygen species‑associated markers (malondialdehyde content and superoxide dismutase activity assays) and the mRNA and protein expression levels of antioxidant genes [nuclear factor (erythroid‑derived 2)‑like 2, manganese superoxide dismutase and heme oxygenase 1] by qPCR and western blot analysis. The results demonstrated that significant destruction of the gut mucosa, delayed small intestinal motility, intestinal barrier dysfunction, and increased inflammatory responses and oxidative stress occurred rapidly in response to ICH. These symptoms occurred as early as 2 h after ICH and persisted for 7 days. These findings suggested that ICH may induce immediate and persistent damage to gut structure and barrier function, which may be associated with upregulation of inflammation and oxidative stress markers.

Glutamine protects intestinal mucosa and promotes its transport after burn injury in rats

Glutamine is an important energy source for intestinal epithelial cells (IEC); however, it is still controversial whether glutaminecan be fully utilized under pathological conditions. In this study, we investigated the changes in glutamine transport after burns and assessed the effects of exogenous glutamine administration. Finally, the potential underlying mechanisms were explored. Experimental rats were randomly divided into three groups: control group (C); burn group (B); burn+glutamine group (B+G). Rats in groups B+G and B received intragastric administration of isodose glutamine or alanine, respectively. At days 1, 3 and 5 after burns, the structure of intestinal mucosa and brush-border membrane vesicles (BBMV) were observed. The glutamine transport capacity of IEC and BBMV was detected. The synthesis of glutamine transporter ASCT2 and B0AT1 was determined. Moreover, the intestinal mucosal blood flow (IMBF), diamine oxidase activity, and the glutamine and ATP content were measured. The results showed that burn injury caused structural damage to IECs and BBMV, and significantly impaired the ability for glutamine transportation. Moreover, the mRNA and protein expressions of ASCT2 and B0AT1 as well as the glutamine and ATP content were markedly decreased. Compared with group B, most of these indicators in group B+G showed significant improvement, and approached normal levels. We conclude that glutamine administration can relieve intestinal damage, improve IMBF, promote energy synthesis and alleviate endoplasmic reticulum stress after burn injury. Finally, the synthesis and modification of ASCT2 and B0AT1 are promoted, which ultimately enhances intestinal glutamine transport.

200mM hypertonic saline resuscitation attenuates intestinal injury and inhibits p38 signaling in rats after severe burn trauma

BACKGROUND

An overabundant discharge of inflammatory mediators plays a significant role in intestinal injury throughout the early stages of critical burns. The present study aims to explore the outcome of 200mM hypertonic saline (HS) resuscitation on the intestinal injury of critically burned rats.

MATERIALS AND METHODS

Fifty-six Sprague-Dawley rats were randomized into three groups: sham group (group A), burn plus lactated Ringer's group (group B), and burn plus 200mM HS group (group C). Samples from the intestine were isolated and assayed for wet-weight-to-dry-weight (W/D) ratio, histopathology analyses, and p38 mitogen-activated protein kinase (MAPK) activity. Serum interleukin 1β (IL-1β) and high mobility group protein box 1 (HMGB1) concentrations were also examined.

RESULTS

Initial resuscitation with 200mM Na⁺ HS significantly decreased the intestinal W/D ratio and improved intestinal histopathology caused by severe burn. HS resuscitation also inhibited the increase of serum IL-1β and HMGB1 concentrations, and p38 MAPK activity in the intestine of critically burned rats.

CONCLUSIONS

The overall findings of this study suggest that preliminary resuscitation with 200mM HS after severe thermal injury reduces intestinal edema, inhibits systemic inflammatory response, and attenuates intestinal p38 MAPK activation, thus reduces burns-induced intestinal injury.

Dysregulation of microRNA biogenesis in the small intestine after ethanol and burn injury

Ethanol exposure at the time of burn injury is a major contributor to post-burn pathogenesis. Many of the adverse effects associated with ethanol and burn injury are linked to an impaired intestinal barrier. The combined insult causes intestinal inflammation, resulting in tissue damage, altered tight junction expression, and increased intestinal permeability. MicroRNAs play a critical role in maintaining intestinal homeostasis including intestinal inflammation and barrier function. Specifically, miR-150 regulates inflammatory mediators which can contribute to gut barrier disruption. The present study examined whether ethanol and burn injury alter expression of microRNA processing enzymes (Drosha, Dicer, and Argonaute-2) and miR-150 in the small intestine. Male mice were gavaged with ethanol (~2.9g/kg) 4h prior to receiving a ~12.5% total body surface area full thickness burn. One or three days after injury, mice were euthanized and small intestinal epithelial cells (IECs) were isolated and analyzed for expression of microRNA biogenesis components and miR-150. Dicer mRNA and protein levels were not changed following the combined insult. Drosha and Argonaute-2 mRNA and protein levels were significantly reduced in IECs one day after injury; which accompanied reduced miR-150 expression. To further determine the role of miR-150 in intestinal inflammation, young adult mouse colonocytes were transfected with a miR-150 plasmid and stimulated with LPS (100ng/ml). miR-150 overexpression significantly reduced IL-6 and KC protein levels compared to vector control cells challenged with LPS. These results suggest that altered microRNA biogenesis and associated decrease in miR-150 likely contribute to increased intestinal inflammation following ethanol and burn injury.

The Effects of Alcohol Intoxication and Burn Injury on the Expression of Claudins and Mucins in the Small and Large Intestines

Alcohol intoxication at the time of burn injury exacerbates postburn pathogenesis. Recent findings suggest gut barrier integrity is compromised after combined alcohol and burn insult, which could contribute to these complications. Tight junction proteins and mucins play critical roles in keeping the gut barrier intact. Therefore, the goal of this study was to examine the effects of alcohol and burn injury on claudin and mucin expression in the intestines. We also evaluated if the combined insult differentially influences their expression in the small and large intestines. Male C57BL/6 mice were given a single dose of 2.9 g/kg ethanol before an approximately 12.5% body area burn. One and three days after injury, we profiled expression of several tight junction proteins, mucin, and bacterial 16S rRNA genes in the small and large intestines, using qPCR. We observed >50% decrease in claudin-4 and claudin-8 genes in both ileal and colonic epithelial cells 1 day after injury. Claudin-2 was significantly upregulated, and occludin was downregulated in the small intestine 1 day after injury. Mucin-3 expression was substantially elevated (>50%) in the small intestine, whereas mucin-2 and mucin-4 were considerably diminished in the colon (>50%) 1 day after injury. Most of the parameters were normalized to sham levels on day 3, except for mucin-3 and claudin-8, which remained decreased in the large intestine. Neither alcohol nor burn alone resulted in changes in junction or mucin gene expression compared to shams. This was accompanied with increases in the family of Gram-negative bacteria, Enterobacteriaceae, in both the small and the large intestines 1 day after injury. These findings suggest that alcohol and burn injury disrupts the normal gut microbiota and alters tight junction and mucin expression in the small and large intestines.